This invention relates to an ink jet where the ink within the jet is of the phase change type which may be referred to as hot melt ink.
The phase change or hot melt ink of the type utilized in an ink jet is characteristically solid at room temperature. When heated, the ink will melt to a consistency so as to be jettable. A hot melt ink jet apparatus and method of operation are disclosed in copending application Ser. No. 610,627, filed May 16, 1984. The hot melt ink may be jetted from a variety of apparatus including those disclosed in the aforesaid copending application.
When employing ink in a liquid state, the delivery of ink is, of course, dictated by the liquid state. Typically, the ink is contained within a closed vessel of some sort prior to delivery to the ink jet. When employing hot melt ink, the delivery of the ink requires different solutions in order to provide a reliable supply and minimize operator intervention. At the same time, it is undesirable to heat an entire supply of hot melt ink at all times since the extended cooking of the hot melt ink may result in degradation of the ink.
In copending application Ser. No. 660,655, filed Oct. 15, 1984, a melt-on-demand system for supplying ink to a reservoir carried by an ink jet imaging head is disclosed. By melting the ink on demand, extended cooking of the ink is avoided as well as the resulting degradation of ink. The amount of ink which may be utilized in such a system is limited by the amount of ink which may be carried on the imaging head.
In copending application Ser. No. 661,701, filed Oct. 16, 1984, a fixed or stationary supply of solid state ink is periodically heated on demand so as to deliver melted ink to a smaller reservoir carried by the imaging head. Such an apparatus avoids extended cooking of the ink in the solid state supply. At the same time, it is not necessary to carry a large volume of ink in the solid state as well as the liquid state in the reservoir carried by the imaging head since the reservoir of the imaging head may be replenished with liquid ink on a periodic basis by moving to a position of coupling to the solid state ink supply.
In accordance with the invention of the aforesaid copending application Ser. No. 661,701, replenishing of the reservoir carried by the imaging head must await the heating of the solid state ink in the solid state ink supply. In other words, a supply of melted ink is not available for instantaneous replenishing of the imaging head reservoir on demand.